JPH111027A - Led array, print head, and electrophotographic printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED which radiates a large amount of light and has a small connection resistance to a p-side electrode. SOLUTION: An LED 10 has an opening part 16 in an interlayer insulating film 12 formed on an n-type semiconductor substrate. A p-type diffusion region is formed at a substrate region corresponding to the opening part 16. A p-side electrode 14 is formed to be connected with the p-type diffusion region. The LED 10 is thus constituted. The LEDs 10 are arranged linearly with a pitch P, thereby forming an LED array. In order to make both a resolution and uniformity of radiation light compatible, a breadth W0 of a surface part 17 which is a substrate surface region of the p-type diffusion region is set to satisfy 0.4P<=W0<=0.5P. An area SO of the surface part 17, an area S2 of a covering part 17a which is an area of the p-side electrode 14 covering the surface part 17, and an area S3 of a connecting part 16a which is an area of the p-side electrode 14 connected to the p-type diffusion region are set to satisfy 0.25S0<=S2<=0.5S0 and S3>=0.4S2 so as to make the amount of radiation light large and a connection resistance of the p-side electrode 14 small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic printer, a print head used as an exposure light source for a photosensitive drum in the electrophotographic printer, and an LED array used for the print head and the like.
Super high density L of 00 [DPI] ([Dot / Inch]) or more
For ED arrays.

[0002]

2. Description of the Related Art FIGS. 19 to 21 are structural views showing an example of a conventional LED array, FIG. 19 is a top structural view of a conventional LED array, FIG. 20 is a top structural view of an LED 50 in FIG. 21 is a sectional view taken along the line CC ′ in FIG. 19 to 21, the LED array 4
1 is a configuration in which a large number of LEDs 50 having individual p-side electrodes 54 are linearly arranged.

The LED 50 has an opening 56 formed by opening an interlayer insulating film 52. Here, zinc (Zn), which is a p-type impurity, is applied to n corresponding to the opening 56 of the interlayer insulating film 52.
The p-type diffusion region 53 is formed by diffusing the p-type diffusion region 53 into the region of the mold substrate 51, and a pn junction 61 that causes a light emission phenomenon is formed by the p-type diffusion region 53 and the substrate 51. The p-side electrode 54 is connected to the p-type diffusion region 53 at the opening 56. Here, the p-side electrode 54 is
It is formed so as to cover a part of the diffusion region surface portion 57 that emits the emitted light, including the connection portion 56a with the mold diffusion region 53. The common n-side electrode 55 is formed on the entire back surface of the substrate 51. By causing a current to flow between the p-side electrode 54 and the n-side electrode 55, a light-emitting phenomenon occurs at the pn junction 61, and emitted light is radiated outside from a portion not covered by the p-side electrode 54.

Here, for example, an LED of 400 [DPI]
In the case of an array, the pitch of the LEDs is about 63 [μm]. In this case, the opening 56 has a width of 30 [μm] × a length of 40.
[Μm]. Further, since the p-type impurity also diffuses in the lateral direction, the diffusion region surface portion 57 has a width of about 40 μm × length of about 50 μm. The connection portion 56a needs to have a certain area in order to reduce the connection resistance,
The area of the connection portion 56a is, for example, 150 [μm ² ]. In this case, the ratio of the area of the covering portion 57a, which is the region of the p-type diffusion region 53 covered by the p-side electrode 54, to the area of the diffusion region surface portion 57 (hereinafter, referred to as the covering ratio) is 0.1. It is about 1.

[0005]

However, in the LED array having the above-described structure, the LED pitch is set to 1200 [D
In the case of ultra-high density of [PI] or more, the p-type diffusion region 53 is finely formed in accordance with the pitch in order to secure insulation from an adjacent LED and to separate adjacent light. Accordingly, the area of the connecting portion 56a also becomes smaller. Connection part 5
When the area of 6a becomes small, there is a problem that the connection resistance increases. On the other hand, if the p-side electrode 54 is formed so that the area of the connection portion 56a is increased, there is a problem that the coverage increases and the amount of radiation decreases.

The present invention solves such a conventional problem, and provides an LED array having a large amount of radiation and a low connection resistance of a p-side electrode even at an ultra high density of 1200 [DPI] or more. The purpose is to do.

[0007]

In order to achieve the above object, an LED array according to the present invention comprises an interlayer insulating film formed on a semiconductor substrate of a first conductivity type, and an opening formed in the interlayer insulating film. An LED having a second conductive type diffusion region formed in a region corresponding to the opening of the semiconductor substrate, and an individual electrode connected to the diffusion region. In the LED array, the width dimension W0 in the pitch direction of the diffusion region surface portion, which is the substrate surface region of the diffusion region, is 0.4P ≦ W0 ≦
0.5P or a width W1 of the opening in the pitch direction satisfies 0.3P ≦ W1 ≦ 0.4P.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment FIGS. 1 to 3 are structural views showing an LED array 1 according to a first embodiment of the present invention. FIG. 1 is a top view of the LED array 1, and FIG. 2 is a top view of an LED 10 in FIG. FIG. 3
FIG. 3 is a sectional view taken along line AA ′ in FIG. 1 to 3
The LED array 1 of the first embodiment shown in FIG.
[DPI] LED array.

In FIG. 1 to FIG.
Represents N (N is a positive integer) L on the n-type semiconductor substrate 11.
The EDs 10-1 to 10-N are arranged in a straight line at a pitch dimension P corresponding to 1200 [DPI]. LED
Reference numeral 10 denotes an n-type semiconductor substrate 11, which is common to the LEDs 10-1 to 10-N, an interlayer insulating film 12 in which an opening 16 is individually formed, and an individually formed p-type diffusion region 13, The formed p-side electrode 14 and the LEDs 10-1 to 10
−N and an n-side electrode 15 formed in common. The p-type diffusion regions 13-1 to 13 -N are formed linearly at a pitch P on the semiconductor substrate 11. Here, the auxiliary number “−k” (k is any integer from 1 to N) indicates the arrangement order on the n-type semiconductor substrate 11. For example, LEDs 10-k and 10- (k + 1)
Are arranged side by side. p-type diffusion region 13-k
And 13- (k + 1) are formed on the semiconductor substrate 11 at an interval Wd.

Next, the manufacturing process of the LED array 1 shown in FIGS. 1 to 3 will be briefly described. FIG. 4 is a cross-sectional structure diagram illustrating an example of a manufacturing process of the LED array 1.
In the manufacturing process shown in FIG. 4, the p-type diffusion region 13 in the LED 10 of the LED array 1 is formed by a Zn solid phase diffusion method.
To form

First, as shown in FIG. 4A, an insulating film serving as a selective diffusion mask 32 is formed on the surface of an n-type semiconductor substrate 11, and this insulating film is patterned to form an opening 16 and a selective diffusion mask. A mask 32 is formed. n-type semiconductor substrate 1
As 1, for example, a GaAs substrate having an n-type GaAs epitaxial layer formed on its surface is used. As the insulating film (selective diffusion mask 32), for example, an aluminum nitride film (AlN film) is used. This AlN film is formed by a sputtering method, and its thickness is, for example, about 2000 [Å].

Next, as shown in FIG.
A Zn diffusion source film 34 is formed on the surface of the n-type semiconductor substrate 11 on which is formed, and an annealing cap film 35 is further formed thereon. As the Zn diffusion source film 34, for example, a ZnO—SiO ₂ mixed film is formed. This ZnO-S
The iO ₂ mixed film is a film obtained by mixing zinc oxide (ZnO) and silicon oxide (SiO ₂ ) at a ratio of 1: 1 and is formed by a sputtering technique. As the annealing cap film 35, for example, a silicon nitride film (SiN film) formed by a CVD technique is used. The thickness of the ZnO-SiO ₂ mixed film is, for example, about 1000 [Å], and the thickness of the SiN film is, for example, about 1000 [１０００].

Next, the n-type semiconductor substrate 11 on which the annealing cap film 35 has been formed is subjected to high-temperature annealing,
Zn is diffused from the n-diffusion source film 34 into the n-type semiconductor substrate 11. In the opening 16, Zn is the n-type semiconductor substrate 1.
In the region where the diffusion mask 12 is formed, Zn does not diffuse in the region where the diffusion mask 12 is formed. Therefore, the p-type diffusion region 13 is selectively formed in a portion corresponding to the opening 16 of the n-type semiconductor substrate 11. You. The conditions for the high-temperature annealing are, for example, an annealing temperature of 700 [° C.] and an annealing time of 2 hours. With this annealing condition, the diffusion depth is 1 [μm],
A p-type diffusion region 13 having a surface Zn concentration of 10 ²⁰ [cm ⁻³ ] is formed. By using the Zn solid phase diffusion method, the p-type diffusion region 13 having a small diffusion depth and low surface sheet resistance (high surface Zn concentration) can be formed, so that the LED 10 with high luminous efficiency is manufactured. it can. In addition,
The annealing cap film 35 prevents Zn from diffusing into the annealing atmosphere.

Here, the region on the substrate surface of the p-type diffusion region 13 is referred to as a diffusion region surface portion 17. Since Zn diffuses not only in the depth direction but also in the lateral direction, the area of the diffusion region surface portion 17 is larger than the area of the opening portion 16.

Next, as shown in FIG. 4C, in the n-type semiconductor substrate 11 on which the p-type diffusion region 13 has been formed, the diffusion source film 34 and the annealing cap film 35 formed on the surface are, for example, The entire surface is removed by wet etching, leaving only the selective diffusion mask 32. An etchant that does not etch the selective diffusion mask 32, such as buffered hydrofluoric acid, is used. The remaining selective diffusion mask 32 is used as it is as the interlayer insulating film 12. Further, an insulating film may be further laminated on the remaining selective diffusion mask 32, and this laminated film may be used as the interlayer insulating film 12.

Next, as shown in FIG.
On the surface of the n-type semiconductor substrate 11 from which the n-type semiconductor substrate 4 and the annealing cap film 35 have been removed, a conductive film to be the p-side electrode 14 is formed, and the conductive film is patterned to form the p-side electrode 14.
To form The p-side electrode 14 is formed so that a part thereof overlaps the opening 16 and the surface 17 of the diffusion region. In the opening 16, the p-side electrode 14
Ohmic connection to the mold diffusion region 13. Therefore, as the above-mentioned conductive film, a film which can be ohmic-connected to the p-type diffusion region 13, for example, an Al film is used.

Here, the p-side electrode 1 is formed in the opening 16.
A connection region between the P. 4 and the p-type diffusion region 13 is referred to as a connection portion 16a. Further, the p-side electrode 1
4 is referred to as a coating portion 17a, and the p-side electrode 1
The portion not covered by 4 is referred to as a light emitting portion 17b. LED
When the device 10 operates, a light emission phenomenon occurs at the interface 31 between the p-type diffusion region 13 and the n-type semiconductor substrate 11. In the light emitting section 17b, the emitted light is emitted to the outside. In the covering section 17a, the emitted light is emitted to the p-side electrode 1.
4 and is not radiated to the outside. Note that the interlayer insulating film 12 transmits the above-described light.

Then, as shown in FIG. 4E, the back surface of the n-type semiconductor substrate 11 is polished, and a conductive film serving as the n-side electrode 15 is formed on the entire back surface of the polished n-type semiconductor substrate 11. Film. As this conductive film, for example, an Au alloy film formed by a sputtering method is used. LED
Array 1 is manufactured.

Next, the dimensions of each part of the LED 10 shown in FIGS. 2 and 3 will be described. As mentioned above, 120
The pitch P corresponding to 0 [DPI] is about 21 [μm]. Therefore, the LEDs 10 are arranged on the n-type semiconductor substrate 11 at a pitch P of about 21 [μm]. In the following description, a dimension in the arrangement direction (pitch direction) of the LEDs 10 is referred to as a width dimension, and a dimension in a direction perpendicular to the arrangement direction is referred to as a length dimension. Also, the arrangement direction of the LEDs 10 is referred to as a width direction,
The direction orthogonal to the arrangement direction is called the length direction.

The LED 10 has a width W 2 of the p-side electrode 14.
Is the width W0 of the diffusion region surface 17 and the opening 16
Is larger than the width W1, the width of the covering portion 17a is equal to the width W0, and the width of the connecting portion 16a is larger than the width W1.
A structure that matches 1. The p-side electrode 14 has a shape that completely covers one side of the rectangular diffusion region surface portion 17 in the pitch direction.

First, the width dimension of each part, particularly the width dimension W0 of the diffusion region surface part 17 and the width dimension W1 of the opening part 16 will be described. The LED array 1 forms a print head together with a lens and the like, and this print head forms an electrophotographic printer together with a photosensitive drum and the like. The resolution and light source uniformity of an electrophotographic printer depend on the characteristics of the lens,
The distance Wd between the diffusion region surface portions 17 in the LED array 1
, Etc. Here, MTF, which is a method for evaluating the performance of an optical system, is used as an index indicating the resolution. LED
Since the LED integration density of the array 1 is 1200 [DPI], the pitch P of the diffusion region surface portion 17 is about 2 as described above.
Since the pitch P is 1 [μm] and the pitch P is determined, the width W0 of the diffusion region surface portion 17 may be determined to determine the distance Wd between the diffusion region surface portions 17. The width W0 of the diffusion area surface portion 17 is set to a value that allows both the resolution (in this example, indicated by MTF) of the electrophotographic printer constituted by using the LED array 1 and the light source uniformity.

FIG. 5 is a diagram for explaining the MTF and the light source uniformity of the electrophotographic printer, and shows the light intensity distribution on the surface of the photosensitive drum when the photosensitive drum is exposed by the print head. (A) LE of LED array 1
This is the light intensity distribution when every other D10 emits light, and (b) is the light intensity distribution when every LED 10 emits light. In FIG. 5, the coordinates x (k−
2), x (k-1), x (k), x (k + 1), x (k
+2) are coordinates in the main scanning direction,
0- (k-2), 10- (k-1), 10-k, 10-
It corresponds to the spot center of the radiated light from (k + 1) and 10− (k + 2). The light intensity is normalized.

In FIG. 5A, the LED 10- (k
-2), 10-k and 10- (k + 2) emit light,
The LEDs 10- (k-1) and 10- (k + 1) do not emit light. A, B, and C are LEDs 10- (k-
2) Intensity distribution characteristics of light emitted from 10-k, 10- (k + 2) are shown, and the sum of characteristics A, C, and B shows the intensity distribution of exposure light from the print head. In this case, if the light intensity of the coordinates x (k−2), x (k), x (k + 2) is 1, and the light intensity of the coordinates x (k−1), x (k + 1) is 0, it is ideal. And the electrophotographic printer is 1200
[DPI] can be completely resolved (however, the above resolution also depends on the material of the photosensitive drum). As the width W0 of the diffusion region surface portion 17 increases, the characteristics A, C, B
Is widened, and when characteristics A, C, and B overlap, x (k
-1), the light intensity at x (k + 1) is no longer 0,
The resolution of the electrophotographic printer is reduced. That is, MTF
Becomes smaller.

In FIG. 5B, E, F, and G are LEDs 10- (k-1), 10-k, 10- (k +
1 shows the intensity distribution characteristics of the light emitted from 1), and H shows the intensity distribution of the exposure light from the print head (the sum of the characteristics E, F, G, etc.). In this case, if the characteristic H is constant regardless of the coordinates, the uniformity of the light source of the electrophotographic printer is ideal (however, the uniformity of the light source also depends on the material of the photosensitive drum). As the width W0 of the diffusion region surface portion 17 becomes narrower, the widths of the characteristics E, F, and G become narrower and the characteristics H become uneven, and the uniformity of the light source decreases. As described above, the MTF and the light source uniformity of the electrophotographic printer have a mutually contradictory relationship from the viewpoint of the width W0 of the diffusion region surface portion 17.

FIG. 6 shows the relationship between the width W0 of the diffusion region surface portion 17 in the LED array 1 and the MTF of the electrophotographic printer using the LED array 1, and the width W0 of the diffusion region surface portion 17 and the light source uniformity of the electrophotographic printer. It is a figure showing the relation with once. In FIG. 6, the MTF and the light source uniformity are respectively normalized, and the horizontal axis is not the width W0 of the diffusion region surface portion 17, but W0 / P. I is M
TF characteristics are shown, and J shows light source uniformity characteristics. It can be considered that the characteristics I and J shown in FIG. 6 do not change even when the value of the pitch P changes. Further, although the characteristics I and J also depend on the characteristics of the lens, it can be considered that they are not largely influenced by the lens characteristics. From FIG. 6, the MTF decreases as W0 / P increases. As described above, the resolution of an electrophotographic printer decreases as the MTF decreases. When the resolution is reduced, the printing becomes blurred or the like, and the printing quality is degraded. Although it depends on the materials such as the photosensitive drum and the developer, according to the experimental data of the inventors, the MFT value is 0.4
In the above case, it is difficult to determine the blur of the print. Therefore, to obtain an MTF value of 0.4 or more from the MTF characteristics of FIG. 6, W0 / P may be set to 0.5 or less. Also, from FIG. 6, the light source uniformity increases as W0 / P increases, and is substantially saturated when W0 / P is around 0.5. In the electrophotographic printer, when the uniformity of the light source is reduced, unevenness or the like occurs in printing, and the printing quality is deteriorated. Although it depends on the material such as the photosensitive drum and the developer, according to the experimental data of the inventors, it is difficult to determine the printing unevenness when the light source uniformity is 0.4 or more. Therefore, to obtain a light source uniformity of 0.4 or more from the light source uniformity characteristic of FIG. 6, W0 / P
Should be set to 0.4 or more. As described above, from the viewpoint of the print quality of the electrophotographic printer, the diffusion region surface 1
If the width W0 of No. 7 satisfies the following expression: 0.4P ≦ W0 ≦ 0.5P (1), it is considered that the MTF of the electrophotographic printer and the light source uniformity can be compatible.

The pitch P of the LED array 1 is about 21 [μ]
m], the width W0 of the diffusion region surface portion 17 is
Referring to equation (1), for example, 10 [μm] (= 4.7)
P). Incidentally, at this time, the interval Wd between the diffusion region surface portions 17 is 11 [μm]. The width W0 of the diffusion region surface 17 (or the distance Wd of the diffusion region surface 17)
) Indicates the p-type diffusion region 13- of the diffusion region surface portion 17-k.
It must be a value that can maintain the insulation between k and the p-type diffusion regions 13- (k-1) and 13- (k + 1) adjacent to the p-type diffusion region 13-k. W0 = above
10 [μm] is a value that can ensure insulation from the adjacent diffusion region.

The width W1 of the opening 16 is expressed as W1 = W0-2xs (2) using the lateral diffusion dimension xs when the p-type diffusion region 13 is formed. As described in FIG. 4, the p-type diffusion region 1
Assuming that the diffusion depth dimension xj of No. 3 is 1 [μm], the lateral diffusion dimension xs is about the same as xj and about 1 [μm]. Therefore, the width W1 of the opening 16 is 8
[Μm]. From the expressions (1) and (2), the relationship between the width W1 of the opening 16 and the pitch P is as follows: 0.4P-2xs≤W1≤0.5P-2xs (3) Here, P is about 21 [μm], 2 × s = 2
[Μm], 2xs = 0.1P, and substituting this into (3) gives the following equation: 0.3P ≦ W1 ≦ 0.4P (4) That is, the width W1 of the opening 16 may be set so as to satisfy (3) or (4). Further, the width W2 of the p-side electrode 14 may be set to a value larger than the width W0 of the diffusion region surface portion 17 in consideration of a mask alignment error in the photolithography process.

Next, the length dimension and area of each part, that is, the length dimension L0 and area S0 of the diffusion region surface portion 17,
The area S1 of the opening 16, the length Le of the light emitting portion 17b,
The length L2 and the area S2 of the covering portion 17a, the connecting portion 1
The area S3 of 6a will be described.

Here, the area may be determined by fixing the area S0 of the diffusion region surface portion 17 and the area S1 of the opening 16 or by fixing the area Se of the light emitting portion 17b. But the area S2 of the covering portion 17a
The covering rate (S2), which is the ratio of the diffusion area surface portion 17 to the area S0 of the diffusion region surface portion 17 (hereinafter, simply referred to as covering area S2)
/ S0) increases as the area S3 (hereinafter simply referred to as the connection area S3) of the connection portion 16a increases, and the connection resistance increases as the connection area S3 decreases. As the coverage increases, the radiation efficiency of light generated at the bonding surface 31 to the outside decreases, and the amount of radiation of the LED 10 decreases.
This is because light generated under the coating portion 17a is
This is because the light is not emitted to the outside due to light shielding by the light source 4. Also,
The driving voltage of the LED 10 (the voltage applied between the p-side electrode 14 and the n-side electrode) is usually constant. Therefore, when the connection resistance increases, the photoelectric conversion efficiency decreases, and the emission light intensity of the LED 10 decreases.

FIG. 7 shows an example of the relationship between the connection area and the connection resistance when the area of the diffusion region surface portion 17 is constant, and FIG. 8 shows an example of the relationship between the connection area and the coverage. FIG. 9 is a diagram illustrating an example of the relationship between the coverage and the amount of radiation of the LED. The vertical axes in FIGS. 7 to 9 are normalized. 7 and 8,
The connection resistance starts to increase sharply when the connection area falls below a certain value, and the coverage increases linearly with an increase in the connection area. Therefore, the connection resistance starts to increase rapidly when the coverage falls below a certain value. Further, in FIG. 9, the amount of radiation of the LED decreases linearly with an increase in the coverage. FIG.
0 is a diagram illustrating an example of the relationship between the above-described coverage and connection resistance, and the relationship between the coverage and the amount of radiation. Note that FIG.
The vertical axis in each is normalized and shown. FIG.
In the case where the coverage is smaller than 0.25, the connection resistance sharply increases. Since the driving voltage of the LED 10 is a constant voltage, when the coverage is smaller than 0.25, the voltage applied between the p-type diffusion region 13 and the n-type substrate 11 becomes small, and the intensity of the emitted light rapidly decreases (however, Since the coverage is also small, the amount of radiated light peaks out). Also, the higher the coverage, the lower the amount of radiation. When the amount of radiation decreases, the exposure energy to the photosensitive drum in the electrophotographic printer decreases, so that the print density decreases and the print quality deteriorates. From FIG. 10, the light amount when the coverage is 0.5 is 0.8 (relative value), which is approximately 10 when compared with the light amount 0.9 (relative value) when the coverage is 0.25.
[%]. This is a range that can be corrected according to the driving conditions. If the coverage is smaller than 0.5, the print quality does not deteriorate. Therefore, in FIG. 10, the area where the connection resistance is small and the amount of radiated light is large has a coverage of 0.2.
The area is 5 to 0.5.

From FIG. 10, the area S0 of the diffusion region surface portion 17 and the area S2 of the covering portion 17a may be determined so as to satisfy the following expression: 0.25S0≤S2≤0.5S0 (5). Here, after determining the area Se of the light emitting portion 17b, the area S0 and the covering area S2 of the diffusion region surface portion 17 are determined by the equation (5).

The length Le of the light emitting portion 17b is, for example, the same as the width W0 of the diffusion region surface portion 17 so that the light emitted from the light emitting portion 17b has a good light emitting spot shape close to a perfect circle.
0 [μm]. Therefore, the area Se of the light emitting section 17b is 100 [μm ² ]. The length L2 of the covering portion 17a is
For example, if it is 5 [μm], the length L0 of the diffusion region surface portion 17 is 15 [μm], and the covering area S2 is 50 [μm].
² ], and the area S0 of the diffusion region surface portion 17 is 150 [μm].
Becomes At this time, S2 = 0.3S0, which satisfies the expression (5).

Since the lateral diffusion dimension xs of the p-type diffusion region 13 is 1 [μm] as described above, the area S 1 of the opening 16 is 8 [μm] × 13 [μm] = 104 [μm].
m ² ], and the connection area S 3 is 8 [μm] × 4 [μm] = 32
[Μm ² ].

Here, the area S2 of the covering portion 17a = 50.
[Μm ² ] and the connection area S3 = 32 [μm ² ].
2 = 1.6S3. As the proportion of the connection area S3 occupied by the connection area S2 increases, the radiated light amount of the LED increases by an amount corresponding to the decrease in the connection resistance for the same coverage area S2. Therefore, in addition to the condition of the expression (5), a condition of S3 ≧ 0.4S2 (6) is further provided. Equation (6) is set by adding a margin of 0.2S2 from the relationship between S2 and S3 in the LED 10.

Further, S2 = 0.3S in the LED 10
0 and the expression (6), the diffusion region surface 1
Deriving the condition consisting of the area S0 of 7 and the connection area S3, S3 ≧ 0.1S0 (7).

Further, the coating area S 2 = 50 [μm ² ],
Since the area S1 of the opening 16 is 104 [μm ² ], S2
= 0.5S1. Using this and the equation (6), the condition consisting of the area S1 of the opening 16 and the connection area S3 is derived, and S3 ≧ 0.2S1 (8). As described above, the area S0 and the covering area S2 of the diffusion region surface portion 17 satisfy Equations (5) and (6), Equations (5) and (7), or Equations (5) and (8). The connection area S3 may be determined.

The diffusion depth xj of the p-type diffusion region 13
Is that if it is too shallow, the surface resistance increases, and if it is too deep,
Since the ratio of the light generated in step 1 to be emitted to the outside decreases, it is determined in consideration of these points. When the p-type diffusion region 13 is formed by the Zn solid phase diffusion method, the diffusion depth xj
Is 1 [μm], and the surface resistance can be sufficiently reduced.

As described above, according to the first embodiment, the relationship between the pitch P and the width W0 of the diffusion region surface portion 17 or the relationship between the pitch P and the width W1 of the opening 16 is expressed by the formula (1) or (1). The LEDs 10 are arranged so as to satisfy the expression (4), the relationship between the area S0 of the diffusion region surface portion 17 and the covering area S2 satisfies the expression (5), and the relationship between the connection area S3 and S2, S3 And S0, the relationship between S3 and the area S of the opening 16
By forming the LED 10 so that any one of the relations with 1 satisfies the expression (6), the expression (7), or the expression (8), the light emitting portion is finely formed in accordance with the ultra-high density pitch. Nevertheless, the amount of radiation can be increased by reducing the coverage, and the connection resistance can be reduced by increasing the connection area. Further, if an electrophotographic printer is configured using the LED array of the first embodiment, an electrophotographic printer having a high resolution MTF and a good light source uniformity can be realized.

The manufacturing process of the LED array according to the first embodiment is not limited to the process shown in FIG. 4, and the insulating film material and the electrode material are also changed to the material shown in FIG. It is not limited. Further, the shapes of the p-side electrode 14 and the diffusion region surface portion 17 are not limited to those shown in FIGS. 1 to 3, and the expressions (5) and (6)
It is optional within a range that satisfies any of formulas (1) to (8).

Second Embodiment FIGS. 11 and 12 show an LED according to a second embodiment of the present invention.
FIG. 11 is a structural view of LEDs in an array, FIG. 11 is a top structural view of LEDs in an LED array of the second embodiment,
FIG. 12 is a sectional structural view taken along line BB 'in FIG. The LED array of the second embodiment has a capacity of 1200
[DPI] LED array.

The LED array according to the second embodiment has an N-type semiconductor substrate 11 having a structure shown in FIGS.
(N is a positive integer) LEDs 20 (20-1 to 20-
N) are linearly arranged at predetermined intervals. LE
D20-1 to 20-N are arranged on the n-type semiconductor substrate 11 with a pitch dimension P corresponding to 1200 [DPI].

The LEDs 20 include LEDs 20-1 to 20-N
N-type semiconductor substrate 11 which is common to
Is formed, an individually formed p-type diffusion region 13, an individually formed p-side electrode 24,
N-side electrode 1 commonly formed in EDs 20-1 to 20-N
5. 11 and FIG.
, The same components as those in FIGS. 1 to 3 are denoted by the same reference numerals. That is, the LED 20 in the second embodiment is the same as the LED 10 in the first embodiment.
In contrast, the LED array of the second embodiment differs from the LED array of the first embodiment in that the diffusion region surface portion 17 is not linear, The configuration is arranged in a straight line. The LED array according to the second embodiment is manufactured by the manufacturing process shown in FIG. 4, for example, similarly to the LED array according to the first embodiment.

Next, the LED 2 shown in FIGS.
The dimensions of each part of 0 will be described. The pitch P is the first
The size and area of the diffusion region surface 17 and the opening 16 are the same as those of the first embodiment.

The LED 20 has a width W 4 of the p-side electrode 24.
Is smaller than the width W1 of the opening, and the p-side electrode 24 is
And a structure formed so as to penetrate the diffusion region surface portion 17 in the length direction. Therefore, the covering portion 27a is formed at the center of the diffusion region surface portion 17 through the diffusion region surface portion 17 in the length direction, and the light emitting portions 27b are formed on both sides in the width direction of the covering portion 27a. The length of the light emitting portion 27b and the length of the covering portion are both the length L0 of the diffusion region surface portion 17.
(= 15 [μm]), and the width of the covering portion is p-side electrode 2
4 equal to the width W4. If the length of the light emitting portion 27b is blindly increased, the resolution in the sub-scanning direction of the electrophotographic printer (MTF is used as an index in this example) is reduced. There is.

The width W4 of the p-side electrode 24 is, for example, 4 [μ
m]. As described above, the length of the covering portion 27a is 15 [μm] and the width of the covering portion 27a is W4, so the area (covering area) S2 of the covering portion 27a is 60 [μm].
² ]. The area S0 of the diffusion region surface portion 17 is 150
Since [μm ² ], S2 = 0.4S0. This relationship between S2 and S0 satisfies the condition of equation (5). The area Se of the light emitting section 27b is 90 [μm ² ].

Since the length of the connection portion 26a is 13 [μm], which is the same as the length of the opening portion 16, the area (connection area) S3 of the connection portion 26a is 52 [μm ² ]. Diffusion area surface 17
Area S0 = 150 [μm ² ], covering area S2 = 60
[Μm ² ], area S1 of opening 16 = 104 [μm ² ]
Therefore, S3 = 0.9S2 = 0.3S0 = 0.5S1. The relationship between S3 and S2, S0, S1 is (6)
Equations (7) and (8) are satisfied.

In the LED 20, the ratio of the connection area S3 to the covering area S2 is larger than that of the LED 10 in the first embodiment. That is, for the same covering area S2, the LED 20 is
The connection area S3 can be made larger than that.

As described above, according to the second embodiment, the width of the p-side electrode 24 is formed smaller than the width of the opening 16, and the p-side electrode 24 penetrates the opening 16 and the diffusion region surface 17. With this configuration, the connection area can be made larger than that of the first embodiment without increasing the covering area, so that the amount of radiated light can be further increased and the connection resistance can be reduced.

In the second embodiment, the p-side electrode is formed so as to penetrate the diffusion region surface portion 17 in the length direction. However, the shape of the p-side electrode is not limited to this. For example, the shape may be as shown in FIG. In FIG. 13A, the p-side electrode 24a is formed so as to partially cover one side of the diffusion region surface portion 17 and the opening 16 in the width direction. In FIG. 13B,
The p-side electrode 24b is connected to the diffusion region surface 17 and the opening 1
6 is formed so as to partially cover one side in the length direction. Further, in FIG. 13C, p is not included in the opening 16 but in the region included in the diffusion region surface 17.
By reducing the width of the side electrode 24c, the area of a portion not included in the connection portion but included in the covering portion is reduced.

Third Embodiment FIGS. 14 to 16 show an LED according to a third embodiment of the present invention.
FIG. 14 is a structural diagram showing the array 7, and FIG.
Top view showing the whole structure, FIG. 15 is an LED in FIG.
FIG. 16 is an enlarged top structural view showing an array end LED 80 located at the end of the array, and FIG. 16 is a cross-sectional structural view taken along the line DD ′ in FIG. LED array 7 of the third embodiment
Is an LED array of 1200 [DPI]. 14 to 16, the same components as those in FIGS. 1 to 3 are denoted by the same reference numerals.

The LED array 7 of the third embodiment has N (N is a positive integer) LEDs 70 on the n-type semiconductor substrate 11.
(70-1 to 70-N) are linearly arranged with a pitch dimension P corresponding to 1200 [DPI]. FIG.
, The LEDs 70-1 and 70-N correspond to the array end LEDs 80 (80a, 80b).

A plurality of (for example, 1000) LED arrays are formed on an n-type semiconductor wafer by the manufacturing process shown in FIG.
After being formed, the chip is cut out into a desired chip size by, for example, a general dicing method. The above-mentioned LED array cut into chips, that is, an LED array formed by arranging a plurality of LEDs on a common n-type semiconductor substrate is particularly called an LED array chip, and an LED array in which a plurality of LED chips are linearly arranged. Or an LED array in which a plurality of LED array chips are linearly arranged. The LED array 7 shown in FIG. 14 is an LED array chip. In FIG. 14, the long side array end 71
Is a chip end in a direction horizontal to the arrangement of the LEDs, and the short side array end 72 is a chip end in a direction perpendicular to the arrangement of the LEDs. Further, the array end 81 (81a,
81b) is a chip end in the extension direction of the LED array, and the short side array end 72 corresponds to this. In the following description, the array end 81 on the array extension side is simply referred to as the array end 81.

The LED 70 includes all the LEDs 70-1 to 70-7.
An n-type semiconductor substrate 11 common to 0-N, an interlayer insulating film 12 in which an opening 16 is individually formed, a separately formed p-type diffusion region 13, and a separately formed p-side electrode 14
And an n-side electrode 15 commonly formed in the LED 70. That is, the LED 70 has the same configuration as the LED 10 in the first embodiment,
The LED array 7 of the embodiment has an array end LED 80 (LE
D70-1, 70-N) and the peripheral structure around the array end 81 (short side array end 72).

Next, the dimension W10 from the center of the array end LED 80 to the array end 81 shown in FIGS. 15 and 16 will be described below. In the LED array 7,
The pitch dimension P of the LEDs 70-1 to 70-N is about 21 [μm], which is the same as that of the first embodiment.
, That is, the dimensions and area of the diffusion region surface portion 17, the opening 16, and the p-side electrode 14 are the same as those in the first embodiment. The pitch dimension P is about 21 [μ]
m], for example, when the number N of the LEDs 70 is 256, the long side dimension of the LED array 7 is about 5 [mm] (about 2 mm).
1 [μm] × 256).

Here, the LED shown in FIGS.
A case where the array 7 (LED array chip) is used for a print head of an electrophotographic printer will be described with reference to FIG. FIGS. 17A and 17B are top views showing a schematic structure of a print head in which the LED arrays 7 are arranged in a straight line. FIG. 17A is a top view of the entire print head, and FIG.
FIG. 7 is an enlarged top view of the periphery of an array end LED 80 and an array end 81 of the array 7.

The print head shown in FIG.
And M (M is an integer of 2 or more) LED arrays 7-1 to 7-M arranged in a row on a wiring board 90, and a drive IC (not shown) for controlling the light emitting operation of the LED array 7
And a lens (not shown) for focusing light from the LED array 7 on a photosensitive drum (not shown). In FIG. 17B, the array end LED 80a and the array end 81a are arranged on the left side of the LED array 7 in the array end LE.
D80 and array end 81, and array end LED 8
0b and the array end 81b indicate the array end LED 80 and the array end 81 on the right side of the LED array 7. The pitch Pch between the arrays is set to
(H-1) and 7-h (h is an arbitrary integer from 2 to M)
, The array end LED of the LED array 7- (h-1)
This is the pitch dimension between the array end LED 80a of the LED array 80b and the LED array 7-h. In the following description, LED
The pitch dimension P of the LEDs 70 in the array 7 is referred to as an array pitch dimension.

As shown in FIG. 17A, the LED array 7 has a light source having the same length as the width Y of the sheet.
They are arranged in a line on the wiring board 90. For example, A4
When corresponding to the size paper, the width Y (width) of the A4 paper is about 210 [mm], and if the length (long side dimension) of the LED array 7 is about 5 [mm] as described above, about What is necessary is just to arrange 40 LED arrays 7. At this time,
The pitch Pch between arrays shown in FIG. 17B also needs to be approximately the same as the pitch P in the array.

The reason will be described with reference to FIG. FIG.
FIG. 8 is a diagram showing a relationship between an inter-array pitch dimension Pch and an emission light intensity distribution in the print head shown in FIG. 17, and the LED arrays 7- (h-1) and 7-h are adjacent to each other. (H-1) LED 70- (N
-1) and the array end LED 80b (LED 70-N), and the array end LED 80a (LED 7
0-1) and the light intensity distribution when all the LEDs 70-2 emit light. FIG. 18A shows a pitch Pc between arrays.
h is larger than the pitch dimension P in the array.
Q shows the total light intensity distribution obtained by integrating the ED light intensities. FIG. 18B shows a case where the inter-array pitch dimension Pch is smaller than the in-array pitch dimension P, and R shows the total light intensity distribution obtained by summing the light intensity of each LED.

As shown in FIG. 18 (a), when the inter-array pitch dimension Pch is larger than the intra-array pitch dimension P, the degree of overlap of the light intensity distribution between the array end LEDs 80 is reduced. The total light intensity between the LED arrays having the pitch dimension Pch is lower than the total light intensity inside the array. The total light intensity between LED arrays decreases as the array pitch Pch increases. The portion of the print head where the overall light intensity distribution Q is reduced causes a decrease in density in printing, and deteriorates print quality. Although it depends on the material of the photosensitive drum and the developer, according to the experimental data of the present inventors, when the pitch dimension Pch between arrays exceeds 1.4 P with respect to the pitch dimension P within the array, a decrease in density in printing is recognized. Therefore, it is necessary to set the pitch dimension Pch between arrays to 1.4P or less.

Further, as shown in FIG. 18B, when the inter-array pitch dimension Pch is smaller than the intra-array pitch dimension P, the degree of overlap of the light intensity distribution between the array end LEDs 80 increases, so that the pitch dimension Pch The total light intensity between the LED arrays having the pitch dimension Pch is higher than that inside the LED array having the pitch Pch. The light intensity between the LED arrays increases as the pitch Pch between the arrays decreases. The portion of the print head where the total light intensity distribution R is increased causes an increase in density in printing and deteriorates print quality. Although it depends on the material of the photosensitive drum and the developer, according to the experimental data of the present inventors, when the pitch dimension Pch between arrays is less than 0.6P with respect to the pitch dimension P in the array, the density increase in printing is caused. To be recognized, it is necessary to set the inter-array pitch dimension Pch to 0.6 P or more.

That is, in a print head in which the LED arrays 7 are arranged in a row, if the pitch dimension Pch between the LED arrays satisfies the following equation: 0.6P ≦ Pch ≦ 1.4P (9) And a good print quality can be obtained without a decrease or increase in the density of.

The pitch Pch between the arrays is
The pitch dimension between the adjacent array end LED 80b and the array end LED 80a in the LED arrays 7- (h-1) and 7-h, and the array end LE shown in FIGS.
Dimension W from center of D80 to array end 81 on array extension side
The relationship with 10 is Pch ≧ 2W10. Here, when the LED arrays are arranged in a line in the print head,
The LED array 7 (LED array chip) may be arranged so as to satisfy the above expression (9). In this case, if the LED arrays 7 (LED array chips) are arranged close to each other, the array end (chip end) is damaged by impact or the like, and In this case, the damage reaches the p-type diffusion region 13 of the array end LED 80, and a defect such as a decrease in the amount of radiation occurs. Therefore, as shown in FIG.
It is necessary to provide a gap Gch between the ED arrays 7 and arrange them. The gap Gch has only to be a dimension such that the LED arrays 7 do not come into contact with each other and are not damaged, and usually 2 [μm] or more is sufficient. Since 2 [μm] = 0.1 P for the pitch P in the array of about 21 [μm], the following equation holds: Pch ≧ 2W10 + 0.1P (10) Therefore, from the relationship between the expressions (9) and (10), 0.25P ≦ W10 ≦ 0.65P (11) is obtained.

However, the lower limit of the dimension W10 from the center of the array end LED 80 to the array end 81 is limited by the dimension of the diffusion region surface portion 17 in addition to the expression (11). The array end 81 is the p-type diffusion region 1 of the array end LED 80
3 (when a part of the p-type diffusion region 13 is cut off), characteristic defects such as a decrease in the amount of radiation are caused. Must be located outside. In the LED array 7, the width W2 of the p-side electrode 14 is set to
Is larger than the width W0 of the array end 81.
Does not enter the inside of the p-type diffusion region 13, the characteristics of the array end LEDs 80 do not deteriorate. The dimension W11 from the edge on the array end 81 side of the diffusion region surface portion 17 to the array end 81 and the diffusion region surface portion 1
If a width W0 of 7 is used, a dimension W10 from the center of the array end LED 80 to the array end 81 is W10 = W0 / 2 + W11. W11 <0 when the array end 81 enters the inside of the p-type diffusion region 13 of the array end LED 80, W11 = 0 when the array end 81 matches the above-mentioned edge of the diffusion region surface portion 17, Assuming that W11> 0 when it is outside, the lower limit of W11 for preventing the characteristic of the array end LED 80 from deteriorating is:
As described above, the edge of the diffusion region surface portion 17 and the array end 81
Since W11 = 0 when が coincides, W10 ≧ W0 / 2 (12). Here, since the upper limit of W0 is 0.5P according to the equation (1), W10≥W0 / 2 = 0.25P (13). As can be seen by comparing the expressions (13) and (11), the LED array 7 satisfying the expression (11) is (1)
Equation 3) is also satisfied.

Since the pitch P in the array of the LED array of 1200 [DPI] is about 21 [μm], the dimension W10 from the center of the array end LED 80 to the array end 81 is
According to the equation (11), the distance may be set in the range of 5 [μm] ≦ W11 ≦ 14 [μm].

As described above, according to the third embodiment, the relationship between the pitch W and the dimension W10 from the array end LED 80 to the array end 81 satisfies the expression (11).
Are arrayed to form the LE of the third embodiment.
If a print head is configured using the D array 7 and an electrophotographic printer is configured using the print head, L
An electrophotographic printer capable of providing good print quality with uniform density even between ED arrays can be realized.

The LED 70 according to the third embodiment
May be the same as that of the second embodiment.
That is, L in the LED array 7 of the third embodiment
The structure of the ED 70 is arbitrary, and the dimension W10 from the array end LED 80 to the array end 81 should satisfy the expression (11).

[0067]

As described above, according to the LED array of the present invention, although the light emitting portion is finely formed according to the ultra-high-density pitch, the amount of radiation can be increased by reducing the coverage. Therefore, there is an effect that the connection resistance can be reduced by increasing the connection area.

Further, according to the print head and the electrophotographic printer constituted by using the above-mentioned LED array, the resolution (the MTF is used as an index in the above embodiment) and the uniformity of the light source are good. There is an effect that a photographic printer can be realized.

[Brief description of the drawings]

FIG. 1 is a top structural view of an LED array according to a first embodiment of the present invention.

FIG. 2 is a top structural view of the LEDs in the LED array according to the first embodiment of the present invention.

FIG. 3 is a sectional structural view taken along line A-A 'in FIG.

FIG. 4 is a cross-sectional structure diagram illustrating an example of a manufacturing process of the LED array of the present invention.

FIG. 5 is a view for explaining resolution (MTF) and light source uniformity in an electrophotographic printer using an LED array.

FIG. 6 is a diagram illustrating an example of a resolution (MTF) characteristic and a light source uniformity characteristic in an electrophotographic printer using an LED array.

FIG. 7 is a diagram illustrating an example of a relationship between a connection area and a connection resistance in an LED.

FIG. 8 is a diagram illustrating an example of a relationship between a connection area and a coverage in an LED.

FIG. 9 is a diagram showing an example of the relationship between the coverage and the amount of radiation in an LED.

FIG. 10 is a diagram showing an example of the relationship between the coverage, the amount of light, and the connection resistance in an LED.

FIG. 11 is a top structural view of an LED in an LED array according to a second embodiment of the present invention.

FIG. 12 is a sectional structural view taken along the line BB ′ in FIG. 11;

FIG. 13 is a top structural view of another LED in the LED array according to the second embodiment of the present invention.

FIG. 14 is a top structural view of an LED array according to a third embodiment of the present invention.

FIG. 15 is a top structural view of an LED in an LED array according to a third embodiment of the present invention.

FIG. 16 is a sectional structural view taken along the line DD ′ in FIG. 15;

FIG. 17 is a top view showing a schematic structure of a print head in which LED arrays according to a third embodiment of the present invention are arranged in a straight line.

18 is a diagram illustrating an example of a relationship between a pitch dimension between arrays and an intensity distribution of emitted light in the print head illustrated in FIG. 17;

FIG. 19 is a top structural view of a conventional LED array.

FIG. 20 is a top structural view of an LED in a conventional LED array.

21 is a sectional structural view taken along the line CC ′ in FIG.

[Explanation of symbols]

1,7 LED array, 10,20,70 LED,
11 n-type semiconductor substrate, 12 interlayer insulating film, 13
p-type diffusion region, 14, 24, 24a, 24b, 24
cp side electrode (individual electrode), 16 opening, 16
a, 26a connection portion, 17 diffusion region surface portion, 17
a, 27a coating part, 80 array end LED, 81
Array end on array extension side, 90 wiring board.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroshi Hamano 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (15)

[Claims] An interlayer insulating film formed on a semiconductor substrate of a first conductivity type; an opening formed in the interlayer insulating film;
LEDs composed of a diffusion region of the second conductivity type formed in a region corresponding to the opening of the semiconductor substrate and individual electrodes connected to the diffusion region are linearly arranged at a predetermined pitch dimension P. The LED array according to claim 1, wherein a width dimension W0 in a pitch direction of a surface of the diffusion region, which is a substrate surface region of the diffusion region, satisfies 0.4P ≦ W0 ≦ 0.5P. 2. An interlayer insulating film formed on a semiconductor substrate of a first conductivity type; an opening formed in the interlayer insulating film;
LEDs composed of a diffusion region of the second conductivity type formed in a region corresponding to the opening of the semiconductor substrate and individual electrodes connected to the diffusion region are linearly arranged at a predetermined pitch dimension P. An LED array according to claim 1, wherein a width dimension W1 of said opening in a pitch direction satisfies 0.3P ≦ W1 ≦ 0.4P. 3. An interlayer insulating film formed on a semiconductor substrate of a first conductivity type, an opening formed in the interlayer insulating film,
LEDs composed of a diffusion region of the second conductivity type formed in a region corresponding to the opening of the semiconductor substrate and individual electrodes connected to the diffusion region are linearly arranged at a predetermined pitch dimension P. In the LED array, the area S2 of the covering portion, which is a region where the individual electrode covers the surface of the diffusion region which is the substrate surface region of the diffusion region, is:
An LED array which satisfies 0.25S0≤S2≤0.5S0 with respect to the area S0 of the surface of the diffusion region. 4. The LED array according to claim 1, wherein an area S2 of a covering portion, which is a region in which the individual electrode covers a diffusion region surface portion, which is a substrate surface region of the diffusion region, is the same as that of the LED array. An LED array which satisfies 0.25S0≤S2≤0.5S0 with respect to the area S0 of the surface of the diffusion region. 5. The LED array according to claim 3, further comprising: an area S3 of a connection portion, which is a region where the individual electrode is connected to the diffusion region in the opening,
The LED array satisfies S3 ≧ 0.4S2 with respect to the area S2 of the covering portion. 6. The LED array according to claim 3, wherein an area S3 of a connection portion, which is a region where the individual electrode is connected to the diffusion region in the opening, is
The LED array satisfies S3≥0.1S0 with respect to the area S0 of the surface of the diffusion region. 7. The LED array according to claim 3, wherein an area S3 of a connection portion, which is a region where the individual electrode is connected to the diffusion region in the opening, is
The LED array satisfies S3 ≧ 0.2S1 with respect to the area S1 of the opening. 8. An LED array in which LEDs are linearly arrayed at a predetermined pitch dimension P on a semiconductor substrate, and an array adjacent to the array end LED from the center of the array end LED located at the end of the array. An LED array, wherein a dimension W10 in the pitch direction up to the extension-side array end satisfies 0.25P ≦ W10 ≦ 0.65P. 9. L according to any one of claims 1 to 7,
In the ED array, the dimension W10 in the pitch direction from the center of the array end LED located at the end of the array to the array extension side array end adjacent to the array end LED satisfies 0.25P ≦ W10 ≦ 0.65P LED array characterized by the above-mentioned. 10. The LED array according to claim 1, wherein the individual electrode completely covers one side in a pitch direction of a diffusion region surface portion which is a substrate surface region of the diffusion region. An LED array, characterized in that the LED array is formed as follows. 11. The LED array according to claim 1, wherein the individual electrode is located on a surface of a diffusion region that is a substrate surface region of the diffusion region.
An LED array formed so as to partially cover one or two sides. 12. The LED array according to claim 1, wherein the LEDs are formed at a pitch of 1200 [DPI] or more. 13. A wiring board, a plurality of LED array chips linearly arranged on the wiring board, and the LE
Driving IC for controlling light emitting operation of D array chip
13. A print head comprising a lens for focusing light from the LED array chip on a photosensitive drum, wherein the LED array according to claim 1 is used as the LED array chip. A print head. 14. The print head according to claim 13, wherein the first array end L formed on the first LED array chip.
ED and a second LED array adjacent to the first LED array chip.
Of the first array end L
A print head, wherein an inter-array pitch dimension Pch which is a pitch dimension between the second array end LED adjacent to the ED and the pitch dimension P satisfies 0.6P ≦ Pch ≦ 1.4P. 15. A print head, a photosensitive drum having a surface on which an electrostatic latent image is formed by light from the print head, a developing device for developing the electrostatic latent image, and the developed electrostatic latent image And a transfer unit that transfers the print data to a sheet, wherein the print head is configured using an LED array. The LED array according to claim 1, wherein the LED array is used as the LED array. Features an electrophotographic printer.